ICE RAFTING EVENTS OFF CENTRAL WEST GREENLAND: A RECORD OF ICE SHEET RETREAT FROM NORTHERN BAFFIN BAY?

At the end of the Last Glacial Maximum (LGM) Baffin Bay was poised for climatic and environmental change. The Greenland Ice Sheet (GIS) terminated on the continental shelf edge off central West Greenland, while ice streams of the marine-terminating margins of Innuitian and Laurentide ice sheets flowed into northern Baffin Bay (NBB). Hemipelagic sediments in sediment cores from the central West Greenland margin record the past behaviors of both the proximal GIS and the distal NBB ice margins and provide insights into the relative phasing of ice-sheet retreat and the influence of ocean warming in initiating and sustaining retreat. Analyses of lithofacies, ice-rafted debris (IRD), and mineralogy in radiocarbon-dated cores indicate changes in sedimentation processes and provenance, while foraminiferal assemblages document the status of inflow of Atlantic Water via the West Greenland Current (WGC) and the presence/absence of seasonal sea ice and glacial meltwater. We focus on establishing the stratigraphy, timing and paleoceanographic conditions related to three major IRD-rich intervals with an NBB provenance, termed ‘NBB events’. The NBB events are marked by a distinct brown color and a sharp rise in detrital carbonate, especially dolomite, and foraminiferal faunas consistent with inflow of Atlantic Water. The first NBB event began c.14.4 cal ka BP, in the Bølling Interstadial, after the GIS had retreated from the shelf-edge; it ended by 13.8 cal ka BP. This event has been radiocarbon dated in 3 sediment cores (JR175-VC46, -VC29, and 2008029-12PC) along the West Greenland margin. A second, overlying NBB event is well developed in VC29 but is still poorly dated. The uppermost NBB event is recorded in JR175-VC34, -VC35, -VC29, and -12PC. Radiocarbon dates from these cores suggest it began by 11.9 cal ka BP and ended before 10.9 cal ka BP. We hypothesize that the NBB events represent an IRD belt along the Greenland margin associated with strong melting of NBB icebergs at the boundary between the northward flowing WGC and comparatively cold, fresh glacial meltwater that covered northern and western Baffin Bay. A question that remains is how closely does the timing of the NBB events relate to the main phases of Laurentide and Innuitian ice-sheet retreat in Northern Baffin Bay.